GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Document type
Keywords
Publisher
Years
  • 11
    facet.materialart.
    Unknown
    Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges (2014)
    Nature Publishing Group
    In:  Nature, 508 (7497). pp. 508-512.
    Details
    Publication Date: 2019-09-23
    Description: Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth’s history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle–ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500–700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/nature13174
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 12
    facet.materialart.
    Unknown
    Basin modelling of a transform margin setting: structural, thermal and hydrocarbon evolution of the Tano Basin, Ghana (2010)
    Geological Soc. Publ. House
    In:  Petroleum Geoscience, 16 (3). pp. 283-298.
    Details
    Publication Date: 2020-06-15
    Description: This study explores the structural and thermal evolution of the Ghana transform margin. The main objective is to explore how the opening of the Atlantic Ocean and subsequent interaction with the Mid-Atlantic Ridge (MAR) has affected the margin's structural and thermal evolution. Two representative evolution scenarios are described: a reference case that neglects the influence of continental breakup and a second scenario that accounts for a possible heat influx during the passage of the MAR as well as magmatic underplating. These two scenarios have further been analysed for the implications for the hydrocarbon potential of the region. The scenario analysis builds on a suite of 2D realizations performed with TECMOD2D, modelling software for automated basin reconstructions. As the observed stratigraphy is input, the structural and thermal evolution of the basin is automatically reconstructed. This is achieved through the coupling of a lithosphere scale forward model with an inverse algorithm for model parameter optimization. We find that lateral heat transport from the passing MAR in combination with flexure of the lithosphere can explain the observed uplift of the margin. These results were obtained for a broken plate elasticity solution with a relative large value for the effective elastic thickness (Te=15) and necking level (15 km). Lateral heat flow from oceanic lithosphere is clearly visible in elevated basement heat flow values up to 50 km away from the ocean–continent transition (OCT). This influx of heat does not seem to have affected the maturation history along the margin significantly. Only the deepest sediments close to the OCT show slightly elevated vitrinite reflectance in simulations that account for the passage of the MAR. In conclusion, it appears that that lateral heat transport from the oceanic lithosphere is instrumental in shaping the Ghana transform margin but seems to have only limited control on the maturation history.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1144/1354-079309-905
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 13
    facet.materialart.
    Unknown
    The Current Energetics of Earth's Interior: A Gravitational Energy Perspective (2016)
    Frontiers
    In:  Frontiers in Earth Science, 4 (46).
    Details
    Publication Date: 2019-02-01
    Description: The Earth's mantle convects to lose heat (Holmes, 1931); doing so drives plate tectonics (Turcotte and Oxburgh, 1967). Significant gravitational energy is created by the cooling of oceanic lithosphere atop hotter, less dense mantle. When slabs subduct, this gravitational energy is mostly (~86% for whole mantle flow in a PREM-like mantle) transformed into heat by viscous dissipation. Using this perspective, we reassess the energetics of Earth's mantle. We also reconsider the terrestrial abundances of heat producing elements U, Th, and K, and argue they are lower than previously considered and that consequently the heat produced by radioactive decay within the mantle is comparable to the present-day potential gravitational energy release by subducting slabs—both are roughly ~10–12 TW. We reassess possible core heat flow into the base of the mantle, and determine that the core may be still losing a significant amount of heat from its original formation, potentially more than the radioactive heat generation within the mantle. These factors are all likely to be important for Earth's current energetics, and argue that strong plume-driven upwelling is likely to exist within the convecting mantle.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3389/feart.2016.00046
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
    facet.materialart.
    Unknown
    Constraining the global inventory of methane hydrate in marine sediments (2011)
    HWU
    In:  In: Proceedings of the 7th International Conference on Gas Hydrates (ICGH2011). HWU, Edinburgh, UK, 129/1-13.
    Details
    Publication Date: 2019-09-23
    Description: The accumulation of methane hydrate in marine sediments is basically controlled by the accumulation of particulate organic carbon at the seafloor, the kinetics of microbial organic matter degradation and methane generation in marine sediments, the thickness of the gas hydrate stability zone (GHSZ), the solubility of methane in pore fluids within the GHSZ and the ascent of deepseated pore fluids and methane gas into the GHSZ. Our present knowledge on these controlling factors is discussed and new estimates of global sediment and methane fluxes are presented. A new transport-reaction model is applied at a global grid defined by these up- dated parameter values. The model yields an improved and better constrained estimate of the global inventory of methane gas hydrates in marine sediments (3000 ± 2000 Gt of methane carbon).
    Type: Book chapter , NonPeerReviewed , info:eu-repo/semantics/bookPart
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Book chapter
  • 15
    facet.materialart.
    Unknown
    2D and 3D numerical models on compositionally buoyant diapirs in the mantle wedge (2011)
    Elsevier
    In:  Earth and Planetary Science Letters, 311 (1-2). pp. 53-68.
    Details
    Publication Date: 2019-02-01
    Description: We present 2D and 3D numerical model calculations that focus on the physics of compositionally buoyant diapirs rising within a mantle wedge corner flow. Compositional buoyancy is assumed to arise from slab dehydration during which water-rich volatiles enter the mantle wedge and form a wet, less dense boundary layer on top of the slab. Slab dehydration is prescribed to occur in the 80–180 km deep slab interval, and the water transport is treated as a diffusion-like process. In this study, the mantle's rheology is modeled as being isoviscous for the benefit of easier-to-interpret feedbacks between water migration and buoyant viscous flow of the mantle. We use a simple subduction geometry that does not change during the numerical calculation. In a large set of 2D calculations we have identified that five different flow regimes can form, in which the position, number, and formation time of the diapirs vary as a function of four parameters: subduction angle, subduction rate, water diffusivity (mobility), and mantle viscosity. Using the same numerical method and numerical resolution we also conducted a suite of 3D calculations for 16 selected parameter combinations. Comparing the 2D and 3D results for the same model parameters reveals that the 2D models can only give limited insights into the inherently 3D problem of mantle wedge diapirism. While often correctly predicting the position and onset time of the first diapir(s), the 2D models fail to capture the dynamics of diapir ascent as well as the formation of secondary diapirs that result from boundary layer perturbations caused by previous diapirs. Of greatest importance for physically correct results is the numerical resolution in the region where diapirs nucleate, which must be high enough to accurately capture the growth of the thin wet boundary layer on top of the slab and, subsequently, the formation, morphology, and ascent of diapirs. Here 2D models can be very useful to quantify the required resolution, which we find for a 1019 Pa · s mantle wedge to be about 1 km node spacing for quadratic-order velocity elements.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2011.08.043
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
    facet.materialart.
    Unknown
    Are the regional variations in Central American arc lavas due to differing basaltic versus peridotitic slab sources of fluids? (2002)
    GSA, Geological Society of America
    In:  Geology, 30 (11). pp. 1035-1038.
    Details
    Publication Date: 2019-09-23
    Description: Central American arc volcanism shows strong regional trends in lava chemistry that result from differing slab contributions to arc melting. However, the mechanism that transfers slab-derived trace elements into the mantle wedge remains largely unknown. By using a dynamic model for mantle flow and fluid release, we model the fate of three different slab-fluid sources: sediment, ocean crust, and serpentinized mantle. In the open subarc system, sediments lose almost all their highly fluid mobile elements by ∼50 km depth, so other fluid sources are necessary to explain the slab signal in arc-lava compositions. The well-documented transition from lavas with a strong geochemical slab signature (i.e., high Ba/La ratios) found in Nicaragua to lavas with a weaker slab signature (i.e., low Ba/La ratios) erupted in Costa Rica seems easiest to produce by a higher fraction of serpentine-hosted fluids released from the deeply faulted, highly serpentinized lithosphere subducting beneath Nicaragua than from the less deeply faulted, thicker, amphibolitic oceanic-crust and oceanic-plateau lithosphere subducting beneath Costa Rica.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/0091-7613(2002)030〈1035:ATRVIC〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
    facet.materialart.
    Unknown
    Controls of faulting and reaction kinetics on serpentinization and double Benioff zones (2012)
    AGU (American Geophysical Union)
    Details
    Publication Date: 2023-11-08
    Description: The subduction of partially serpentinized oceanic mantle may potentially be the key geologic process leading to the regassing of Earth's mantle and also has important consequences for subduction zone processes such as element cycling, slab deformation, and intermediate-depth seismicity. However, little is known about the quantity of water that is retained in the slab during mantle serpentinization and the pattern of serpentinization that may occur during bending-related faulting; an initial state that is essential for quantifying subsequent dehydration processes. We present a 2-D reactive-flow model simulating hydration processes in the presence of faulting at the trench outer-rise. We find that the temperature dependence of the serpentinization rate in conjunction with outer-rise faulting results in plate age and speed dependent patterns of hydration. Serpentinization also results in a reduction in surface heat flux toward the trench caused by advective downflow of seawater into the reaction region. Observed heat flow reductions are larger than the reduction due to the minimum-water downflow needed for partial serpentinization, predicting that active hydrothermal vents and chemosynthetic communities should also be associated with bend-fault serpentinization. Our model results agree with previous studies that the lower plane of double Benioff zones can be generated due to dehydration of serpentinized mantle at depth. More importantly, the depth-dependent pattern of serpentinization including reaction kinetics predicts a separation between the two Benioff planes consistent with seismic observations.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 18
    facet.materialart.
    Unknown
    Anhydrite‐Assisted Hydrothermal Metal Transport to the Ocean Floor—Insights From Thermo‐Hydro‐Chemical Modeling (2020)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: High‐temperature hydrothermal venting has been discovered on all modern mid‐ocean ridges at all spreading rates. Although significant strides have been made in understanding the underlying processes that shape such systems, several first‐order discrepancies between model predictions and observations remain. One key paradox is that numerical experiments consistently show entrainment of cold ambient seawater in shallow high permeability ocean crust causing a temperature drop that is difficult to reconcile with high vent temperatures. We investigate this conundrum using a thermo‐hydro‐chemical model that couples hydrothermal fluid flow with anhydrite‐ and pyrite‐forming reactions in the shallow subseafloor. The models show that precipitation of anhydrite in warming seawater and in cooling hydrothermal fluids during mixing results in the formation of a chimney‐like subseafloor structure around the upwelling, high‐temperature plume. The establishment of such anhydrite‐sealed zones reduces mixing between the hydrothermal fluid and seawater and results in an increase in vent temperature. Pyrite subsequently precipitates close to the seafloor within the anhydrite chimney. Although anhydrite thus formed may be dissolved when colder seawater circulates through the crust away from the spreading axis, the inside pyrite walls would be preserved as veins in present‐day metal deposits, thereby preserving the history of hydrothermal circulation through shallow oceanic crust.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 19
    facet.materialart.
    Unknown
    The Foundation-PAR plume-ridge interaction: constraints on competing forces and the structure of oceanic líthosphere (2018)
    In:  [Talk] In: GeoBonn 2018, 02.09.-06.09.2018, Bonn, Germany .
    Details
    Publication Date: 2019-04-25
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Talk
  • 20
    facet.materialart.
    Unknown
    Extensional tectonics and two-stage crustal accretion at oceanic transform faults (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Oceanic transform faults are seismically and tectonically active plate boundaries1 that leave scars—known as fracture zones—on oceanic plates that can cross entire ocean basins2. Current descriptions of plate tectonics assume transform faults to be conservative two-dimensional strike–slip boundaries1,3, at which lithosphere is neither created nor destroyed and along which the lithosphere cools and deepens as a function of the age of the plate4. However, a recent compilation of high-resolution multibeam bathymetric data from 41 oceanic transform faults and their associated fracture zones that covers all possible spreading rates shows that this assumption is incorrect. Here we show that the seafloor along transform faults is systemically deeper (by up to 1.6 kilometres) than their associated fracture zones, in contrast to expectations based on plate-cooling arguments. Accretion at intersections between oceanic ridges and transform faults seems to be strongly asymmetric: the outside corners of the intersections show shallower relief and more extensive magmatism, whereas the inside corners have deep nodal basins and seem to be magmatically starved. Three-dimensional viscoplastic numerical models show that plastic-shear failure within the deformation zone around the transform fault results in the plate boundary experiencing increasingly oblique shear at increasing depths below the seafloor. This results in extension around the inside corner, which thins the crust and lithosphere at the transform fault and is linked to deepening of the seafloor along the transform fault. Bathymetric data suggest that the thinned transform-fault crust is augmented by a second stage of magmatism as the transform fault intersects the opposing ridge axis. This makes accretion at transform-fault systems a two-stage process, fundamentally different from accretion elsewhere along mid-ocean ridges.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...